So i've finally implemented the texture manager and the cache. I've also added a simple quadtree that refines the textures based on the distance to the terrain patches. It's working pretty well.
I'm a bit disapointed by the terrain textures though. It looks pretty good in the screenshots, but quite repetitive when you see the whole world with similar texturing. I have to add some variety.
The terrain patches that are far away, especially when you descend at ground level, become "aliased". Adding mipmapping didn't help. It's not a big deal since in the final code they'll most likely be hidden by atmosphere haze, but still, i'd like to improve a bit their look.
Getting nice coastlines is not easy. If i reduce the amplitude of noise to get realistic coastlines, i get a lower quality in the landscape, like in the grass or rock areas. If i increase the noise, coastlines start to become a mess of noisy fractals. To fix that, i'll have to add a per-pixel parameter which determines how noisy the area is.
I can't seem to get good lighting at all scales. If i tweak the parameters to have some nice shading at ground level, the terrain as seen from a few kilometers away becomes noisy, and vice-versa. I think one of the solutions is to drop the lower octaves depending on the camera distance, but implementing that in a pixel shader 2.0.. hum.
Then there is the detail textures, the blending to hide the popping between different texture levels, and a lot of small details like that..